Recently, in consideration of environmental issues, there is a demand for correction fluid containers for storing a correction fluid to be given in a so-called refillable form. To develop a correction fluid container into a refillable form, it is necessary to select a solvent resistant material because methyl cyclohexane, as the main solvent of the correction fluid, has high volatility. It is also necessary to select a material having such transparency that permits the remaining amount of the correction fluid to be monitored.
Conventionally, the correction fluid containers for correction pens are known to be formed by extrusion molding, blow molding, injection molding of nylon resin (c.f. Japanese Patent Application Laid-open 2002-65351) or formed of nylon 12 (c.f. Japanese Patent Application Laid-open 2002-67585), in order to obtain enhanced solvent resistance and inhibit swelling due to the solvent used and reduction of the solvent due to permeation, in comparison with polyethylene and polypropylene.
Molded articles of polyamide resin made from aliphatic monomers, such as nylon 12 and the like, described in these literatures, have solvent resistance, however do not have high enough transparency. Further, the correction fluid tends to adhere to the inner wall surface of the container and does not flow down as the correction fluid is consumed with application, so there are still problems in that the remaining amount cannot be correctly monitored and that it is difficult to use up the charged correction fluid completely.
On the other hand, concerning conventional ballpoint type writing instruments and applicators such as correction pens, some have free liquid type configurations in which ink or correction fluid is directly filled in the barrel, others have configurations in which ink or correction fluid is filled in an ink reservoir (refill) of a refill unit to be accommodated in the barrel. Either of these is configured such that the ballpoint pen tip is directly press fitted into the front end of the barrel or ink reservoir or that the tip holder having a ballpoint pen tip attached to the front part thereof is press fitted at its rear end into the front end of the barrel or ink reservoir filled up with ink.
The front part, of the synthetic resin-made barrel to which the tip holder is press fitted, or of the synthetic resin-made ink reservoir to which the tip is directly press fitted, is always under a condition of being internally stressed. Such a stress and an additional stress which may arise in the ballpoint pen tip during writing or application, in combination, would cause reduction of the press-fitting force on the tip holder or tip with the passage of time, leading to problems such as easy drop-off of the tip holder or tip and liability to ink leaking from the press fitting part.
In order to prevent ink leaking and drop-off of the tip holder of a free liquid type ballpoint pen in which ink is directly stored in a synthetic resin-made barrel, a technology has been known in that the front part of the barrel to which the rear end of the tip holder is press fitted is covered over its outer peripheral surface with a metal tube (c.f. Japanese Patent Application Laid-open 2002-113985).
However, the above configuration on its own, in which the front part of the barrel to which the rear end of the tip holder is press fitted is covered over its outer peripheral surface with a metal tube, cannot be expected to exert a sufficient effect, hence in the above publication the covering metal tube is adapted to be held between a flange of the tip holder and the front end of the barrel to achieve the expected effect.
Further, because of use of the tip holder, parts increase in number, resulting in problems in view of processing accuracy and assembly precision.
Moreover, in a refill unit which has a tip directly press fitted to a synthetic resin-made ink reservoir and is mounted to a ballpoint type applicator whose pen tip can be projected and retracted from the front part of the barrel by a clicking mechanism and which has a pressurizing mechanism in linkage with the clicking action, an additional pressure from the rear end of the ink reservoir is further applied in combination with the internal stresses at the front part of the ink reservoir to which the tip is press fitted and stresses acting on the ballpoint tip during application, hence leading to problems of more likeliness of drop-off of the tip and leaking of correction fluid, than usual.
In view of the above problems in prior art, the present invention is to solve them. The first object is to provide a refill for a correction pen that stores a correction fluid having as the main solvent methyl cyclohexane, which is highly volatile, wherein the refill for a correction pen is excellent in solvent resistance and in transparency and visibility so that the correction fluid stored and its remaining amount can easily be monitered during usage and with the passage of time. The second object is to provide a refill unit which has a tip directly press fitted to a synthetic resin-made ink reservoir (refill) is mounted to an applicator such as a ballpoint type correction pen whose pen tip can be projected and retracted from the front part of the barrel by a clicking mechanism and which has a pressurizing mechanism in linkage with the clicking action, wherein the refill unit is simple in structure and reduced in number of parts and further can prevent the tip from dropping off from the ink reservoir and prevent leaking of ink, correction fluid or the like.